20 Things You Didn’t Know About Time
1 “Time is an illusion. Lunchtime doubly so,” joked Douglas Adams in The Hitchhiker’s Guide to the Galaxy. Scientists aren’t laughing, though. Some speculative new physics theories suggest that time emerges from a more fundamental—and timeless—reality.
2 Try explaining that when you get to work late. The average U.S. city commuter loses 38 hours a year to traffic delays.
3 Wonder why you have to set your clock ahead in March? Daylight Saving Time began as a joke by Benjamin Franklin, who proposed waking people earlier on bright summer mornings so they might work more during the day and thus save candles. It was introduced in the U.K. in 1917 and then spread around the world.
4 Green days. The Department of Energy estimates that electricity demand drops by 0.5 percent during Daylight Saving Time, saving the equivalent of nearly 3 million barrels of oil.
5 By observing how quickly bank tellers made change, pedestrians walked, and postal clerks spoke, psychologists determined that the three fastest-paced U.S. cities are Boston, Buffalo, and New York.
6 The three slowest? Shreveport, Sacramento, and L.A.
7 One second used to be defined as 1/86,400 the length of a day. However, Earth’s rotation isn’t perfectly reliable. Tidal friction from the sun and moon slows our planet and increases the length of a day by 3 milliseconds per century.
8 This means that in the time of the dinosaurs, the day was just 23 hours long.
9 Weather also changes the day. During El Niño events, strong winds can slow Earth’s rotation by a fraction of a millisecond every 24 hours.
10 Modern technology can do better. In 1972 a network of atomic clocks in more than 50 countries was made the final authority on time, so accurate that it takes 31.7 million years to lose about one second.
11 To keep this time in sync with Earth’s slowing rotation, a “leap second” must be added every few years, most recently this past New Year’s Eve.
12 The world’s most accurate clock, at the National Institute of Standards and Technology in Colorado, measures vibrations of a single atom of mercury. In a billion years it will not lose one second.
13 Until the 1800s, every village lived in its own little time zone, with clocks synchronized to the local solar noon.
14 This caused havoc with the advent of trains and timetables. For a while watches were made that could tell both local time and “railway time.”
15 On November 18, 1883, American railway companies forced the national adoption of standardized time zones.
16 Thinking about how railway time required clocks in different places to be synchronized may have inspiredEinstein to develop his theory of relativity, which unifies space and time.
17 Einstein showed that gravity makes time run more slowly. Thus airplane passengers, flying where Earth’s pull is weaker, age a few extra nanoseconds each flight.
18 According to quantum theory, the shortest moment of time that can exist is known as Planck time, or 0.0000000000000000000000000000000000000000001 second.
19 Time has not been around forever. Most scientists believe it was created along with the rest of the universe in the Big Bang, 13.7 billion years ago.
20 There may be an end of time. Three Spanish scientists posit that the observed acceleration of the expanding cosmos is an illusion caused by the slowing of time. According to their math, time may eventually stop, at which point everything will come to a standstill.
How Do You Tell Time On Mars?
Synchronizing rovers on Mars with their drivers on Earth is a bit of a challenge
On the Image: Sunrise At Gale Crater The sun rises over Gale Crater on Mars, the future home of the newest Mars rover, Curiosity. Rover scientists will upload commands overnight — Mars time — so the rover can start its day bright and early. NASA/JPL
When NASA’s new Mars rover lands on the Red Planet this summer, it’s safe to assume it’ll be sometime in the morning or early afternoon at the Jet Propulsion Laboratory in California, home of the rover science and engineering teams. So that means it’ll be mid-afternoon on the East Coast, evening in Europe, and so on — pretty easy to figure out the time zones. But what time will it be on Mars? What time zone will Curiosity live in — and how can you even tell?
Timekeeping on Mars is a bit like telling time on Earth, because the planets are similar in lots of ways. But there are just enough differences to drive a person slightly crazy. To start with, the Martian day, or sol, is 39 minutes and 35 seconds longer than a day on Earth. This isn’t a lot, but it adds up quickly when you’re living on Mars time—as the Curiosity team will. And a Martian year lasts 668.59 sols, about 1.88 times an Earth year. Seasons last much longer and are much more extreme, thanks in part to Mars’ deeply eccentric orbit.
“Time Cloak” Created; Can Make Events Disappear
Experiment is first to make a hole in time, expert says.
A time lens splits light into temporal components similar to a lens splitting white light into colors.
Photograph by GI Photo Stock X/Alamy
Einstein’s theories of relativity suggest that gravity can cause time to slow down. Now scientists have demonstrated a way to stop time altogether—or at least, to give the appearance of time stopping by bending light to create a hole in time.
The new research builds on recent demonstrations of “invisibility cloaks” that can make objects seem to disappear by bending waves of visible light.
The idea is that, if light moves around an object instead of striking it, that light doesn’t get scattered and reflected back to an observer, making the object essentially invisible.
Now Cornell University scientists have used a similar concept to create a hole in time, albeit a very short one: The effect lasts around 40 trillionths of a second.
“Imagine that you could divert light in time—slow it down, speed it up—so that you create a gap in the light beam in time,” said study co-author and Cornell physicist Alex Gaeta.
“In this case, any event that occurs at that instant of time won’t lead to scattering of light. It appears as if the event never occurred.”
(Related: “Space-Time Cloak Possible, Could Make Events Disappear?”)
